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Topic: Sound Calibration
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Steve Guttag
We forgot the crackers Gromit!!!
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Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 01-24-2016 09:13 AM
A key thing that the R2 and now D2 bring to the table, that cannot be over emphasized is that each mic is calibrated AND that on the display they are normalized. That is, the mic nearest the screen will not be over emphasized since it will be receiving a louder signal.
When using other programs (built in CP analyzers or SMAART...etc.) is to consider your source. Lets say you use an awesome set of microphones and preamp...what normalizing those mics? That is, what is keeping each contribution to the spacial average the same?
People like to equate the USL MMP to the D2 because they are similar but they are WAY different. The straight USL mics are not calibrated. At best, USL can apply an RC type compensation to a mic response. With the D2, there is an actual offset file to each microphone that is applied in software so that microphone's response is perfect, not an approximation. When you are applying EQ with a +/- 3dB response and your microphone (each of four, hopefully) already has a few dB variance on the spectrum, that adds into the overall response you will see and compensate for...thus your compensation may be to your microphone(s) as much as your room response.
It is certainly possible to normalize the USL multiplexer on a room-by-room basis...but I seriously doubt that many do...it is too much work to tweak it for each room to get them right...there will be a lot of "good enough" rationalization.
The proof is in the results...take a room that was tuned up with either an R2 or D2 and have someone else put their R2 or D2 system in there after them, even months after and don't tell them where the mics were...the responses will be identical, within ISO 2969. At most, you'll see variations that can be attributed to humidity changes and decay of HF diaphragms.
The D2 is not the end-all in room analysis, it doesn't do impulse response and such but it does do cinema response VERY well and does allow one to measure RT-60 (Reverberation) and NC (noise floor) in addition to traditional RTA functions. One can even do STC measurements though that requires a bit of work on the user to utilize the data collected (plus I've found that one should bring their own external stimuli to ensure a meaningful result is captured).
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